On‐off‐on Control of Molecular Inversion Symmetry via Multi‐stage Protonation: Elucidating Vibronic Laporte Rule
On‐off‐on Control of Molecular Inversion Symmetry via Multi‐stage Protonation: Elucidating Vibronic Laporte Rule
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通过多级质子化控制分子反转对称性：阐明电子拉波尔特规则
DOI：
10.1002/anie.202212581
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Szymański, Bartosz
中科院分区：
文献类型：
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作者：
Stark, Charles W.;Rammo, Matt;Trummal, Aleksander;Uudsemaa, Merle;Pahapill, Juri;Sildoja, Meelis‐Mait;Tshepelevitsh, Sofja;Leito, Ivo;Young, David C.;Szymański, Bartosz
拉波尔特规则规定，反演对称分子的单光子和双光子吸收光谱应显示交替禁止的电子跃迁；然而，对于有机荧光团，由于普遍的电子振动相互作用，对称和非反转对称双光子光谱之间的明确区别常常被模糊。我们利用连续的单质子化和双质子化来打破并重建名义对称二酮吡咯并吡咯的反演对称性，从而导致双光子吸收发生巨大变化。通过进行详细的单光子和双光子滴定实验，并支持量子化学模型计算，我们解释了某些低频振动模式如何导致与严格的拉波特规则的明显偏差。因此，该系统确实可以被视为一种开-关-开反转对称开关，为双光子传感应用开辟了新途径。
The Laporte rule dictates that one‐ and two‐photon absorption spectra of inversion‐symmetric molecules should display alternatively forbidden electronic transitions; however, for organic fluorophores, drawing clear distinction between the symmetric‐ and non‐inversion symmetric two‐photon spectra is often obscured due to prevalent vibronic interactions. We take advantage of consecutive single‐ and double‐protonation to break and then reconstitute inversion symmetry in a nominally symmetric diketopyrrolopyrrole, causing large changes in two‐photon absorption. By performing detailed one‐ and two‐photon titration experiments, with supporting quantum‐chemical model calculations, we explain how certain low‐frequency vibrational modes may lead to apparent deviations from the strict Laporte rule. As a result, the system may be indeed considered as an on‐off‐on inversion symmetry switch, opening new avenues for two‐photon sensing applications.